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| United States Patent |
5,145,180
|
|
Oka
|
September 8, 1992
|
Golf ball
Abstract
A golf ball has dimples arranged in eight spherical equilateral triangles
obtained by projecting, on the imaginary spherical surface of the golf
ball, the ridge lines of a regular octahedron inscribing the imaginary
spherical surface. Three great circles corresponding to the ridge lines
being projected on the spherical surface. One great circle coinciding with
a mold seam is formed as the sole great circle unintersecting dimples and
the other two great circles intersect dimples. Between 300 to 550 dimples
are formed in the golf ball with the dimples being equivalently arranged
in each of the eight spherical equilateral triangles.
| Inventors:
|
Oka; Kengo (Kobe, JP)
|
| Assignee:
|
Sumitomo Rubber Industries, Ltd. (Hyogo, JP)
|
| Appl. No.:
|
668109 |
| Filed:
|
March 12, 1991 |
Foreign Application Priority Data
| Current U.S. Class: |
473/382; 40/327; 473/384 |
| Intern'l Class: |
A63B 037/14 |
| Field of Search: |
273/232,220,62
40/327
|
References Cited
U.S. Patent Documents
| 4744564 | May., 1988 | Yamata | 273/232.
|
| 4848766 | Jul., 1989 | Oka et al. | 273/232.
|
| 4973057 | Nov., 1990 | Morell | 273/232.
|
| 5044638 | Sep., 1991 | Nesbitt et al. | 273/232.
|
| Foreign Patent Documents |
| 0371866 | Jun., 1990 | EP.
| |
| 2-152476 | Jun., 1990 | JP.
| |
| 2176409 | Dec., 1986 | GB.
| |
| 2211743 | Dec., 1989 | GB.
| |
Primary Examiner: Marlo; George J.
Claims
What is claimed is:
1. A golf ball comprising dimples arranged in eight spherical equilateral
triangles obtained by projecting, on an imaginary spherical surface of
said golf ball, the ridge lines of a regular octahedron inscribing said
imaginary spherical surface, between 300 to 550 dimples being provided on
the golf ball, three great circles corresponding to said ridge lines being
projected on said spherical surface, one great circle coinciding with a
mold seam being formed as a sole great circle unintersecting dimples and
the other two great circles intersect dimples, the dimples being
equivalently arranged in each of said eight spherical equilateral
triangles.
2. The golf bass as claimed in claim 1, wherein the dimple specification of
an S spherical zone in a vicinity of said seam and a P spherical zone in a
vicinity of poles are set in the range of 0.95.ltoreq.RS/RP.ltoreq.1.20
for each hemisphere of the golf ball where RS is a value obtained by
dividing the total volume of all dimples arranged in said S spherical zone
by the area of said S spherical zone of said imaginary spherical surface;
and RP is a value obtained by dividing the total volume of all dimples
arranged in said P spherical zone by the area of said P spherical zone of
said imaginary spherical surface.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf ball, and more particularly, to the
golf ball having an octahedral dimple arrangement which improves the
flight performance of the golf ball.
2. Description of the Related Arts
Normally, 300 to 550 dimples are formed on the surface of a golf ball so as
to increase the flight distance thereof by improving the aerodynamic
characteristic thereof. Of various proposals regarding dimple
arrangements, regular octahedral arrangement is most widely adopted
because dimples are arranged symmetrically and regularly.
As shown in FIGS. 10, 11 and 12, according to the regular octahedral
arrangement, the spherical surface of a golf ball 1 is divided into eight
spherical equilateral triangles by projecting, on the spherical surface of
the golf ball 1, the ridge lines 2a of a regular octahedron 2 inscribing
the spherical surface of the golf ball 1 and dimples are equivalently
arranged in each spherical triangle as shown in FIG. 12. The ridge lines
2a projected on the spherical surface of the golf ball 1 form three great
circles 3, 4, and 5 on which dimples 6 are not arranged. That is, the golf
balls 1 has on the surface thereof three great circles which do not
intersect the dimples 6.
Normally, since the golf ball is molded by a pair of upper and lower
semispherical molds, dimples are not arranged on the seam between the
upper and lower molds so as to facilitate the removal of a burr formed
when the golf ball is molded. Therefore, in the regular octahedral dimple
arrangement, the great circle 3 coincides with the seam.
The main object of the dimple is to accelerate the transition of the
turbulent flow of a boundary layer and increase the aerodynamic
characteristic of the golf ball in order to increase the flight distance
of the golf ball. Therefore, it is well known to those skilled in the art
to effectively arrange dimples to accelerate the transition of the
turbulent flow of the boundary layer. From this point of view, various
proposals have hitherto been made to improve the regular octahedral dimple
arrangement on the surface of the golf ball. According to the dimple
arrangement proposed by Japanese Patent Laid-Open Publication No. 62-79072
(unexamined), dimples of large and small diameters are arranged on the
surface of the golf ball. According to the dimple arrangement proposed by
Japanese Patent Laid-Open Publication No. 2-152476 (unexamined), dimples
of more than three different diameters are arranged on the surface of the
golf ball.
The regular octahedral dimple arrangements proposed by these prior patent
applications are capable of improving the flight performance of the golf
ball to some extent, however, there is still a problem due to three great
circles being formed on the golf ball.
Namely, when the golf ball flies with backspin, dimples arranged on a
circumference which rotates fastest in its backspin have the most affect
on the flight distance of the golf ball. When the circumference which
rotates fastest in its backspin coincides or approximately coincides with
a great circle having no dimples arranged thereon, dimple effect is
reduced, so that the flight distance of the golf ball becomes shorter. In
the octahedral dimple arrangement, there is a great possibility that the
circumference which rotates fastest in its backspin coincides or
approximately coincides with one of the three great circles because the
golf ball has three great circles unintersecting dimples. Therefore, the
flight distance of the golf ball is varied due to one of the great circles
formed thereon.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide a golf ball
having a regular octahedral dimple arrangement and a favorable aerodynamic
symmetrical property so as to increase the flight distance thereof by
providing only one great circle unintersecting dimples.
In accomplishing these and other objects, the present invention provides a
golf ball having dimples arranged in eight spherical equilateral triangles
obtained by projecting, on the imaginary spherical surface of the golf
ball, the ridge lines of a regular octahedron inscribing the imaginary
spherical surface. Of three great circles corresponding to the ridge lines
projected on the spherical surface, one great circle coinciding with a
seam between a pair of molds is formed as the sole great circle
unintersecting dimples and the other two great circles intersect dimples.
According to the preferred golf ball, dimples are arranged equivalently in
each of the eight spherical equilateral triangles.
Preferably, each dimple intersecting the two great circles corresponding to
the ridge lines projected on the spherical triangle protrudes from one
spherical equilateral triangle to an adjacent spherical equilateral
triangle in the length of more than 0.3 mm.
In order to equalize to each other the aerodynamic characteristic of the
vicinity of the seam corresponding to the great circle is formed and
unintersecting dimples and the vicinity of the poles having dimples
densely arranged, the surface of the golf ball is divided into an S
spherical zone in the vicinity of the seam and a P spherical zone in the
vicinity of the poles P. The dimple specification of S and P zones are set
so that assuming that RS is a value obtained by dividing the total volume
of all dimples arranged in S zone by the surface area of S zone of the
imaginary spherical surface and RP is a value obtained by dividing the
total volume of all dimples arranged in P zone by the surface area of P
zone of the imaginary spherical surface, RS/RP is set in the range:
0.95.ltoreq.RS/RP.ltoreq.1.20
According to the above construction, since the golf ball has only one great
circle corresponding to the seam not intersecting dimples, the possibility
that a circumference which rotates fastest in its backspin coincides or
approximately coincides with the great circle can be reduced, so that the
flight distance of the golf ball can be increased by improving the
aerodynamic characteristic thereof.
In addition, dimples of larger volumes are arranged in S zone in the
vicinity of the seam on which the great circle unintersecting dimples is
formed. Dimples of smaller volumes are arranged in P zone, in the vicinity
of the poles, in which dimples are densely arranged. Therefore, the
aerodynamic symmetrical property of the golf ball can be improved. That
is, the aerodynamic characteristic of the golf ball is equalized between a
case where a circumference which rotates fastest in its backspin coincides
with the seam and a case where a circumference which rotates fastest in
its backspin coincides with the pole.
Further scope of applicability of the present invention will become
apparent from the detailed description given hereinafter. However, it
should be understood that the detailed description and specific examples,
while indicating preferred embodiments of the invention, are given by way
of illustration only, since various changes and modifications within the
spirit and scope of the invention will become apparent to those skilled in
the art from the detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects and features of the present invention will become
apparent from the following description taken in conjunction with the
preferred embodiments thereof with reference to the accompanying drawings
which are given by way of illustration only, and thus are not limitative
of the present invention, and in which:
FIG. 1A is a plan view showing a golf ball according to the embodiment of
the present invention;
FIG. 1B is a front view showing the golf ball shown in FIG. 1A;
FIG. 2 is a schematic view for explaining a dimple specification;
FIG. 3A is a view showing a design stage of the golf ball according to the
present invention;
FIG. 3B is an enlarged view showing principal portions obtained when
designing of a golf ball has been completed;
FIGS. 4A and 4B are schematic views each showing a manner for forming a
great circle unintersecting dimples;
FIG. 5 is a view showing an enlarged principal portion of FIG. 1A;
FIGS. 6A and 6B are views each showing a modification for intersecting
dimples and a great circle with each other;
FIGS. 7A, 7B, and 7C are views each showing, similarly to FIG. 5, a
modification for intersecting dimples and a great circle with each other;
FIG. 8 is schematic view showing the relationship between P zone and S zone
of the surface of a golf ball;
FIG. 9A is a plan view showing a comparison golf ball;
FIG. 9B is front view showing the golf ball of FIG. 9A;
FIG. 9C is a view showing dimples arranged in a spherical equilateral
triangle of a comparison golf ball;
FIG. 10 is a schematic view showing the concept of regular octahedral
dimple arrangement;
FIG. 11 is a schematic perspective view showing a golf ball having regular
octahedral dimple arrangement; and
FIG. 12 is a plan view showing a golf ball having a conventional regular
octahedral dimple arrangement.
DETAILED DESCRIPTION OF THE INVENTION
Before the description of the present invention proceeds, it is to be noted
that like parts are designated by like reference numerals throughout the
accompanying drawings.
FIG. 1A is a plan view, showing a golf ball 10 according to the present
invention, viewed with the pole P of the golf ball 10 placed uppermost.
FIG. 1B is a front view showing the golf ball 10 shown in FIG. 1A.
Based on a regular octahedron as shown in FIG. 11, dimples 11 are arranged
on the golf ball 10. That is, the seam coincides with one of three great
circles 12, 13, and 14 corresponding to the ridge lines, of a regular
octahedron which inscribes the imaginary spherical surface of the golf
ball 10, projected on the spherical surface of the golf ball 10. That is,
the great circle 12 does not intersect the dimples 11 while the great
circles 13 and 14 intersect the dimples 11.
Since the golf ball 10 has a regular octahedron on, the golf ball 10 has on
the surface thereof eight spherical equilateral triangles I through VIII.
According to this embodiment, dimples 11 are arranged equivalently in each
eight triangles I through VIII. The dimples 11 consist of eight kinds A
through H as shown in Table 1. The diameter of the dimple A is identical
to that of the dimple B. The diameter of the dimple C is identical to that
of the dimple D; the diameter of the dimple E is identical to that of the
dimple F; and the diameter of the dimple G is identical to that of the
dimple H. But the depths, curvatures, and volumes of the dimples A and B
are different from each other; those of the dimple C are different from
those of the dimple D; those of the dimple E are different from those of
the dimple F; and those of the dimple G are different from those of the
dimple H.
As shown in FIG. 2, according to the dimple specification of Table 1,
diameter is the length of a common tangent to both end points (a) and (b)
of the dimple 11; depth is the length longest of perpendiculars dropped
from the above tangent to the surface of the dimple 11, namely, the length
from point (c) to (d); curvature is the radius (R) of a sphere, part of
which forms the surface of the dimple 11; and volume is indicated by
diagonal lines of FIG. 2.
TABLE 1
__________________________________________________________________________
dimple specifications between golf balls of
the present invention and the comparison examples
total
number kind
number
diame- curva-
of of of ter depth
ture
volume
total volume (mm.sup.3)
RS RP RS/
dimples dimple
dimples
(mm)
(mm)
(mm)
(mm)
S zone
P zone
whole
mm.sup.3 /mm.sup.2
mm.sup.3 /mm.sup.2
RP
__________________________________________________________________________
embodi-
410 A 96 4.10
0.16
13.1
1.07
165.9
174.4
340.3
0.123 0.116 1.06
ment B 138 4.10
0.14
14.8
0.95
C 16 3.70
0.16
10.6
0.88
D 32 3.70
0.14
12.0
0.78
E 48 3.20
0.16
8.3 0.63
F 16 3.20
0.14
9.4 0.55
G 40 2.80
0.16
6.3 0.49
H 24 2.80
0.14
7.1 0.43
compari-
416 A 200 3.95
0.17
11.6
1.04
170.6
167.0
337.6
0.109 0.128 0.85
son B 216 3.00
0.17
6.7 0.60
__________________________________________________________________________
According to the golf ball 10, as shown in FIG. 1A, eight kinds of dimples
11 are arranged equivalently in each of the eight spherical equilateral
triangles I through VIII so that the dimples 11 are symmetrical with
respect to each of the great circles 12, 13, and 14 corresponding to the
ridge lines of a regular octahedron inscribing the imaginary spherical
surface of the golf ball 10 on which the ridge lines are projected. More
specifically, each of the great circles 13 and 14 bisects dimples 11-1.
That is, each of the dimples 11-1 on the great circles 13 and 14 is
divided equivalently into two portions by the great circles 13 and 14
respectively and is arranged in adjacent equilateral triangles. While the
dimples 11 which are adjacent to the great circle 12 and are not arranged
on the great circle 12 are symmetrical with respect thereto as shown in
FIG. 1B.
As shown in FIG. 3A, dimples are arranged equivalently in each of the eight
equilateral triangles as follows: First, each of the eight equilateral
triangles formed according to a regular octahedron is divided into six
congruent spherical triangles, so that the spherical surface of the golf
ball is divided into 48 congruent triangles. Then, assuming that one of
the 48 triangles is a unit triangle X, dimples 11 are arranged on each
side X-1, X-2, and X-3 of the triangle X so that they intersect each side
X-1, X-2, and X-3. As shown in FIG. 3B, the dimples 11 are arranged in
each of the 48 unit triangles so that each triangle has the same dimple
arrangement as that of triangle X. According to this design, the golf ball
10 has dimples arranged equivalently in each of the eight spherical
equilateral triangles and no great circles unintersecting dimples.
However, as described above, dimples cannot be arranged on the seam
because it is necessary to remove a burr formed on the seam between a pair
of semispherical upper and lower molds. Therefore, dimples which are to be
formed on the great circle corresponding to the seam are removed as shown
in FIG. 4A or moved as shown in FIG. 4B or a dimple arrangement is
redesigned to form only one seam corresponding to the great circle 12
unintersecting dimples in combination of dimple movement and removal. The
movement or removal of dimples which are to be formed on the seam great
circle corresponding to the seam results in intersections of dimples and
the formation of bald areas. In order to overcome this problem, fine
adjustments such as movements of dimples inside each of the eight
spherical equilateral triangles, size alterations and additions of dimples
are carried out so that dimples are equivalently arranged in each
spherical equilateral triangle.
According to the above method, the golf ball 10 has the great circle 12
corresponding to the seam which does not intersect the dimples 11, two
great circles 13 and 14 intersecting the dimples 11, and the dimples 11
equivalently arranged in each of the eight spherical equilateral
triangles.
As shown in FIG. 5, the length L of the dimple 11 intersecting the great
circles 13 and 14 and protruding from the spherical equilateral triangle I
to the adjacent spherical equilateral triangle II is favorably, more than
0.3 mm, and more favorably, 0.8 mm. In this embodiment, the length L of
the dimple 11 is more than 1.4 mm.
The number of dimples 11-1 which intersect the great circles 13 and 14
respectively is at least two, favorably eight or more, and more favorably,
30 or more. According to this embodiment, 34 dimples 11-1 intersect both
the great circles 13 and 14, respectively.
In addition to the embodiment as shown in FIGS. 1 and 5, dimples may
intersect the great circle 13 and 14 as shown in FIGS. 6A, 6B, FIGS. 7A,
7B, and 7C in which one-quarter of the great circle 13 between the seam 12
and the pole P is shown.
Referring to FIG. 6A, two dimples intersect the great circles 13 and 14,
respectively. In FIG. 6B, eight dimples intersect the great circles 13 and
14, respectively. FIGS. 6A and 6B show an example in which the dimples 11
are equivalently arranged in each of the eight spherical equilateral
triangles.
Referring to FIGS. 7A, 7B, and 7C, the dimples 11-1 are not equivalently
arranged in each of the eight spherical equilateral triangles. FIG. 7A
shows an example in which four dimples 11-1 intersect the great circles 13
and 14, respectively. FIG. 7B shows an example in which the dimples 11-1
intersect the great circles 13 and 14 in three patterns (i), (ii), and
(iii). In pattern (i), the great circle 13 passes through the center of
the dimple 11-1. In pattern (ii), the dimples at the right and left sides
with respect to the great circle intersects the great circles 13 and 14,
respectively, thus projecting from one spherical equilateral triangle to
the adjacent triangle and overlapping with another dimple protruding
similarly. In pattern (iii), the dimple 11-1 projects from one triangle to
the adjacent triangle in a manner similar to the pattern (ii), but the
patter (iii) differs from pattern (ii) in that the dimple 11-1 protrudes
from only one triangle to the other triangle and the projecting length
thereof is less than one-half of the radius thereof. In this embodiment of
FIG. 7B, the great circles 13 and 14 intersect 36 dimples, respectively.
Referring to FIG. 7C, the great circles 13 and 14 intersect 16 dimples,
respectively.
In the golf ball having the great circle 12 formed thereon, when the great
circle 12 coincides or approximately coincides with a circumference which
rotates fastest in its backspin, the dimple effect is reduced and as such,
the trajectory becomes low and the flight distance becomes short. In order
to solve this problem, the following construction is provided: The surface
of the golf ball 10 is divided into two zones, namely, an S spherical zone
in the vicinity of the poles P as shown in FIG. 8. The volume of the
dimple in S zone is greater than that of the dimple in P zone while the
diameters of both dimples are equal to each other. More specifically, as
shown by one-dot chain lines, S zone ranges from the great circle 12 to
each of circumferences formed in correspondence with a central angle
.theta. (10.degree..ltoreq..theta.<60.degree.) with respect to the seam.
As shown by two-dot chain lines, P zone ranges from each of the
circumferences corresponding to the central angle .theta. to the poles P.
Assuming that a value RS is obtained by dividing the total volume of all
dimples arranged in S zone by the surface area of S zone of the imaginary
sphere and that a value RP is obtained by dividing the total volume of all
dimples arranged in P zone by the surface area of P zone of the imaginary
sphere, RS/RP is set as follows:
0.95.ltoreq.RS/RP.ltoreq.1.20
For example, supposing that the dimple A and the dimple B have the same
diameter of 4.1 mm, the greater volume dimple A is arranged in S zone and
the smaller volume dimple B is arranged in P zone.
In this embodiment, the spherical surface of the golf ball is divided into
S zone and P zone at an angle of 30.degree. and the total volume of all
dimples arranged in S zone is 165.9 mm.sup.3. The value RS obtained by
dividing the dimple volume 165.9 mm.sup.3 by the surface area of S zone of
the imaginary sphere is 0.123 mm.sup.3 /mm.sup.2. The total volume of all
dimples arranged in P zone is 174.4 mm.sup.3. The value RP obtained by
dividing the dimple volume 174.4 mm.sup.3 by the surface area of P zone of
the imaginary sphere is 0.116 mm.sup.3 /mm.sup.2. Therefore, RS/RP is 1.06
which satisfies the range between 0.95 and 1.20 as described above. If
RS/RP is less than 0.95, the trajectory of the golf ball becomes low when
the great circle 12 coincides or approximately coincides with a
circumference which rotates fastest in its backspin. If RS/RP is more than
1.20, the trajectory of the golf ball becomes too high.
The reason the central angle .theta. which divides the surface of the golf
ball into S zone and P zone is 10.degree. or more and less than 60.degree.
is as follows: If the central angle .theta. is less than 10.degree.,
dimples are arranged in an extremely small number in S zone. Consequently,
the division of the surface of the golf ball into S zone and P zone has no
meaning and the differentiation of dimple volume has no effect either. If
the central angle .theta. is more than 60.degree., the dimple effect of S
zone is greater than that of P zone, and consequently, the aerodynamic
symmetrical property cannot be improved. Accordingly, the central angle
.theta. is appropriately set at the angle of 10.degree. or more than
10.degree. and less than 60.degree. in consideration of the dimple
arrangement, the construction of the golf ball, and mixing proportion of
materials of the golf ball.
EXPERIMENT 1
The flight performance tests of the golf ball according to the present
invention and comparison golf ball, or conventional golf ball were
conducted.
Comparison golf balls 1 having a dimple specification as shown in Table 1
and FIGS. 9A, 9B, and 9C were prepared. The comparison golf balls 1 have
regular octahedral arrangement and three great circles 3, 4, and 5 not
intersecting dimples. The volume of dimples of the comparison golf balls 1
arranged in S and P zones are not differentiated. Accordingly, RS/RP is as
small as 0.85.
Each of the golf balls according to the present invention as shown in FIG.
1 and comparison golf balls as shown in FIG. 9 has a liquid center wound
with thread covered with a balata cover. Both golf balls have the same
construction and mixing proportion of materials. The outer diameter is
each 42.70.+-.0.03 mm and compression is each 95.+-.2.
Flight test of the balls according to the present invention and comparison
golf balls were conducted using a swing robot manufactured by True Temper
Corp. Balls were hit by a driver (No. 1 wood) at a head speed of 45 m/s.
Spin was 3500.+-.300 rpm and a ball launching angle was 10.+-.0.5.degree..
Wind was fair at a speed of 0.6.about.2.8 m/s.
The number of the golf balls of the embodiment and the comparison golf
balls prepared was 20, respectively. The temperature thereof was kept at
23.degree..+-.1.degree. C. The golf balls of the embodiment and the
comparison golf balls were alternately hit.
The carry, total, and duration of flight of the golf balls of the
embodiment and comparison golf balls shown in Table 2 are the average of
those of 20 golf balls.
"Carry" shown in Table 2 is the distance from a hitting point to a falling
point; "total" is the distance from the hitting point to the point at
which each golf ball stopped; and "trajectory height" is an angle of
elevation viewed from the launching point of each golf ball to the highest
point thereof in trajectory.
TABLE 2
______________________________________
Flight distance test
trajectory flight
carry total height duration
(yard) (yard) (DEG) (SEC)
______________________________________
embodiment
228.5 245.3 13.30 5.30
comparison
224.2 242.0 13.18 5.21
______________________________________
TABLE 3
______________________________________
Symmetrical property test
trajectory
flight
kind of carry total height duration
hitting (yard) (yard) (DEG) (SEC)
______________________________________
embodi-
pole 245.5 260.2 13.72 5.87
ment seam 244.9 260.5 13.67 5.87
compar-
pole 242.6 254.6 13.57 5.79
ison seam 238.8 256.0 13.20 5.46
______________________________________
As shown in Table 2, the golf ball of the embodiment traveled further than
the golf ball of the comparison golf ball by 4.3 yards in carry and by 3.3
yards in "total". It was confirmed from this result that in flight
distance, the golf ball of the embodiment having one great circle formed
thereon is superior to the comparison golf ball having three great
circles.
EXPERIMENT 2
Symmetrical test was conducted on the golf balls according to the
embodiment and the comparison golf balls used in example 1, employing a
swing robot manufactured by True Temper Corp. The golf balls were hit by a
driver at a head speed of 48.8 m/s. Spin was 3500.+-.300 rpm; ball
launching angle was 9.degree..+-.0.5.degree.. Wind was fair at a speed of
0.3.about.2.2 m/s. The number of the embodiment golf balls and the
comparison golf balls was 40 respectively, 20 ball were used each for pole
hitting and seam hitting. The temperature thereof was kept at 23.degree.
C..+-.1.degree. C.
According to seam hitting, a rotational axis is selected so that a
circumference which rotates fastest in its backspin coincides with the
seam. According to pole hitting, a circumference perpendicular to the
rotational axis in seam-hitting functions as the rotational axis of the
backspin.
As shown in Table 3 indicating the result of the symmetrical property test,
the golf balls of the embodiment had little difference in carry, total,
trajectory height, and duration of flight between seam hitting and pole
hitting. On the other hand, according to the comparison golf balls, the
trajectory height in seam hitting was lower than that in pole hitting, and
the duration of flight and carry in seam hitting were shorter than those
in pole hitting.
It was confirmed from the above result that dimple effect is not reduced
even in seam hitting and a golf ball having a favorable symmetrical
property can be obtained owing to the differentiation of dimple volumes in
S zone and P zone as described previously.
That is:
0.95.ltoreq.RS/RP.ltoreq.1.20
As apparent from the foregoing description, without damaging a favorable
symmetrical property and fine view of regular octahedral dimple
arrangement, the golf ball in accordance with the present invention is
capable of achieving a flight performance more favorable than that of the
conventional golf ball. That is, since the golf ball has only one great
circle corresponding to the seam not intersecting dimples, the possibility
that a circumference which rotates fastest in its backspin coincides or
approximately coincides with the great circle is reduced, so that the
flight distance of the golf ball can be increased.
In addition, the surface of the golf ball is divided into two zones. One is
in the vicinity of the great circle unintersecting dimples and the other
is in the vicinity of the poles. The volumes of dimples are differentiated
according to each zone so as to improve the difference in the aerodynamic
symmetrical property of the golf ball between seam hitting and pole
hitting. Accordingly, the trajectory of the golf ball is not varied so
much even though the golf ball spins about a varied rotational axis. As
such, the golf ball is capable of faithfully display a player's ability,
thus contributing to the improvement of player's skill. Further, since the
golf ball has only one great circle corresponding to the seam, an upper
mold is rotated with respect to a lower mold so as to design various
dimple arrangement without affecting the flight performance thereof.
Although the present invention has been fully described in connection with
the preferred embodiments thereof with reference to the accompanying
drawings, it is to be noted that various changes and modifications are
apparent to those skilled in the art. Such changes and modifications are
to be understood as included within the scope of the present invention as
defined by the appended claims unless they depart therefrom.
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